This invention relates to a magnetron anode, and more particularly to a magnetron anode of the type having a plurality of vanes radially provided inside the anode cylinder, and a method for manufacturing the magnetron anode.
Conventionally, a magnetron anode of the type wherein a plurality of vanes are radially integrally provided inside the anode cylinder is manufactured by being subject to only one extrusion-molding process. This manufacturing method, though seemingly thought to be a most efficient method, has the following actual inconveniences. Since the interval S1 between the free ends of two adjacent vanes is extremely narrow as shown in FIG. 1, the thickness of a corresponding portion of the punch for forming said interval S1 is extremely small and accordingly the punch is very low in terms of mechanical strength and therefore irresistible to mass-production. In the case of an ordinary magnetron used in a domestic microwave oven and having, for example, an output having a power of several hundred watts and an oscillating frequency of 2450 MHz, the number of vanes is 12 and said interval S1 is as small as only 1.2 mm. Accordingly, the thickness of a corresponding portion of the punch is only 1.2 mm. Thus, a punch having an extremely low mechanical strength can not but be employed. Further, when the vanemolding sections of the punch are slightly deformed during the manufacturing process, the thicknesses of the vanes become ununiform or the configurations of the free end portions of the vanes become uneven and a magnetron using an anode member with such uneven configurations of vanes becomes unstable in respect of its oscillating characteristics. Also with respect to the anode cylinder, its axial length is as relatively large as about 32 mm in the case of the abovementioned customarily used magnetron, and therefore it is considerably difficult due to a small vane-to-vane's interval to mold such large length of anode cylinder by one pressing process as disclosed, for example, in U.S. Pat. No. 3,719,068.